Just hours after a bloodied 12-year-old Payton Leutner stumbled out of some Waukesha woods saying she'd been stabbed by her friends, police were interviewing Anissa Weier and Morgan Geyser.

"The whole time, Payton was screaming in agony. Saying stuff like, 'I hate you guys. I'll never forgive you, and I trusted you,'" Anissa said during a police interview.

The pair blamed their fixation with the fictional Internet ghoul Slender Man.

"You start to get something that people call Slender Sickness from the sigma radiation that he emits," Morgan said during her interrogation.

Morgan was diagnosed with schizophrenia, but Anissa is also trying a so-called insanity plea, with a twist, suggesting in court filings she was influenced by Morgan's illness to such a degree she became mentally ill as well.

A rare syndrome was first identified in 19th century France named Folie a Deux. The translation to English of the dated term is madness of two.

"He would, or could, kill our families and everything we love. And I don't want that to happen so that's why I did this," Anissa said.